sPHENIX discussion of the superconducting solenoid

[Kin Yip <kinyip AT bnl.gov>]

Hello,

Today, we've completed the test with a 75 A power supply.   Carl and Fred and later with ChaoFeng Mi spent a couple hours to get the power supply to work.  They realized at the
end that their mistake was due to an open circuit :-) Somehow, the real test started after 3 pm.

I attached the plot of magnetic field measurement in our Logger system.   ( John Haggerty has another system. )   It reads > 207 G at 75 A.  ( At the moment, this value is somewhat
smaller than our "hope" of ~1.37 T at 4596 A.  ) 

There was no (mysterious or non-mysterious) temperature jump this afternoon.

We first measured the voltage across the entire superconducting path including the coil.  Here, though we saw inductive voltage ~LdI/dt when the current ramped up, we only saw noisy
voltage when the current was steady,  fluctuating around -ve and +ve tens or a hundred micro-volt  at the same/stable current.  We later measured the "superconducting" path on each side
of the coil (but excluding the coil).   Apparently, the meter gave much more steady voltages in these cases.   There, the small resistance on one side was bigger than the other side, presumably
due to the joints (with the non-superconducting "Indium").  

The suspicious temperature sensors  TT1786/TT1787 on both side read slightly lower than ~25 K at their lowest today.  But the side giving higher resistance (though all are small) actually
read 1 K lower in temperature :-)   We probably need Carl's analysis  but it seems to me that the superconductors were superconducting and the small resistances were due to the joints.

Carl will analyze his data and we'll discuss tomorrow with some experts at 3-4 pm in 902 conf. room.   Hopefully, we'll agree to go ahead so that on Friday, at 1 pm if Cryo conditions
allow,  we can use our "real" power supply and quench detection system to run with the Magnet.  

Fred will help re-connect back the MCM cables with the Current Leads tomorrow.

Kin

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